OFFSET
1,1
COMMENTS
a(n) == 1 (mod 72) for n >= 3. - Hugo Pfoertner, Aug 29 2021
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
a(3) = 28729 is a term because 28729 = 13^4 + 13^2 - 1, and 13 and 28729 are primes.
MAPLE
map(t -> t^4+t^2-1, select(t -> isprime(t) and isprime(t^4+t^2-1), [2, seq(i, i=3..10000, 2)]));
MATHEMATICA
f[p_] := p^4 + p^2 - 1; Select[Map[f, Select[Range[600], PrimeQ]], PrimeQ] (* Amiram Eldar, Aug 29 2021 *)
Select[Table[p^4+p^2-1, {p, Prime[Range[200]]}], PrimeQ] (* Harvey P. Dale, Aug 11 2024 *)
PROG
(Python)
from sympy import isprime, primerange
def auptop(maxp): return list(filter(isprime, (p**4 + p**2 -1 for p in primerange(1, maxp+1))))
print(auptop(580)) # Michael S. Branicky, Aug 29 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, Aug 29 2021
STATUS
approved